What is cortisol?

William D. Knopf, MD
Cardiology (Cardiovascular Disease)
Cortisol belongs to a class of hormones called glucocorticoids, which affect almost every organ and tissue in the body. The most important job of cortisol is to help the body respond to stress. Among its many vital tasks, cortisol helps:
Maintain blood pressure (BP) and cardiovascular function.Slow the immune system's inflammatory response.Maintain levels of glucose-a form of sugar used for energy-in blood.Regulate the metabolism of proteins, carbohydrates, and fats.
The amount of cortisol produced by the adrenals is precisely balanced. Like many other hormones, cortisol is regulated by the brain's hypothalamus and the pituitary gland. First, the hypothalamus releases a "trigger" hormone called corticotropin-releasing hormone (CRH) that signals the pituitary gland. The pituitary responds by sending out adrenocorticotropic hormone (ACTH), which, in turn, stimulates the adrenal glands. The adrenal glands respond by producing cortisol. Completing the cycle, cortisol then signals back to both the pituitary and hypothalamus to decrease these trigger hormones.
This answer is based upon source information from the National Institute of Diabetes and Digestive and Kidney Diseases.
Dr. Kathleen Hall
Preventive Medicine
Cortisol is a stress hormone that has many functions. It is critical for the regulation of our metabolism and the body's use of proteins, carbohydrates, and fats, regulation of blood pressure, and cardiovascular function, and it helps our bodies manage stress. Cortisol is produced by the adrenal glands in response to signals from the pituitary gland and hypothalamus of the brain. The secretion of cortisol increases in response to psychological or physical stress of any kind. Following a stressful event, adrenaline levels return to normal while cortisol levels can remain elevated over a much longer period of time.
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Cortisol is a steriod hormone produced by the adrenal gland. The hormone is released in response to stress and low levels of blood sugar and its primary function is to increase blood sugar levels, suppress the immune system and aid in metabolism. 

Cortisol, a steroid, has three main functions. It causes the liver to produce sugar and causes break down of muscle and fat to create this sugar. Cortisol also helps the body regulate its response to stress. Lastly, cortisol decreases inflammation and decreases the immune system response. Excess steroids can lead to Cushing’s syndrome, obesity, diabetes, high blood pressure, weak muscles, characteristic bodily changes, and brittle bones.
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.